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Date: Mon, 18 Aug 2014 09:37:57 -0700
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: slub/debugobjects: lockup when freeing memory
Message-ID: <20140818163757.GA30742@linux.vnet.ibm.com>
Reply-To: paulmck@linux.vnet.ibm.com
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 <20140619165247.GA4904@linux.vnet.ibm.com>
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To: Christoph Lameter <cl@gentwo.org>
Cc: Thomas Gleixner <tglx@linutronix.de>, Sasha Levin <sasha.levin@oracle.com>, Pekka Enberg <penberg@kernel.org>, Matt Mackall <mpm@selenic.com>, Andrew Morton <akpm@linux-foundation.org>, Dave Jones <davej@redhat.com>, "linux-mm@kvack.org" <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>

On Thu, Jun 19, 2014 at 03:19:39PM -0500, Christoph Lameter wrote:
> On Thu, 19 Jun 2014, Thomas Gleixner wrote:
> 
> > Well, no. Look at the callchain:
> >
> > __call_rcu
> >     debug_object_activate
> >        rcuhead_fixup_activate
> >           debug_object_init
> >               kmem_cache_alloc
> >
> > So call rcu activates the object, but the object has no reference in
> > the debug objects code so the fixup code is called which inits the
> > object and allocates a reference ....
> 
> So we need to init the object in the page struct before the __call_rcu?

And the needed APIs are now in mainline:

	void init_rcu_head(struct rcu_head *head);
	void destroy_rcu_head(struct rcu_head *head);

Over to you, Christoph!  ;-)

							Thanx, Paul

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